CVE-2026-107573: Incorrect Default Permissions in hMailServer
Incorrect default permissions in the Windows installer of Progressive Robot hMailServer 6.0.0 through 6.3.5 allow a local authenticated user to read the mail server's data. The installer created the data, log, temp, database and event folders and the hMailServer.INI configuration file with the permissions inherited from the installation folder, by default under Program Files, which give the local Users group read access. Any user who can sign in to the computer could read every stored message, the logs, the built-in database with the accounts' password hashes whenever the service is stopped, and the configuration file, including the database password, which is sealed only with the machine's DPAPI key and can be unsealed by any local account; with an external database that password gives full control of it. The Linux AppImage of 6.3.0 through 6.3.5 likewise created its per-user data folders readable by other local users.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
hMailServerto a version that resolves this vulnerability.Fixed in 6.3.6 - Configuration
From an elevated prompt, remove the inherited entries for Users and the application package groups using icacls with /inheritance:d, then /remove:g.
hMailServer data, log, temp, database, and event folders plus hMailServer.INI Windows filesystem permissions = Remove inherited Users and application package group entries - Operational
Change the database password and the administrator password if accounts that are not administrators could sign in to the server.